I. Assess and compare the safety and potential toxicities associated with treating patients with metastatic Merkel cell carcinoma (MCC) with either major histocompatibility complex (MHC) up regulation and programmed cell death 1 (PD1)-axis blockade (Group 1), or MHC up-regulation, PD1-axis blockade and adoptive transfer of Merkel cell polyoma virus (MCPyV) T antigen (TAg)-specific polyclonal autologous cluster of differentiation (CD)8+ T cells (Group 2).